One Hundred Years of the Cosmological Constant: from ‘Superfluous Stunt’ to Dark Energy

Posted in History, The Universe and Stuff with tags , , , on November 21, 2017 by telescoper

Some months ago I did a little post on the occasion of the 100th anniversary of the introduction of the cosmological constant which included a link to the original paper on this subject by Albert Einstein. A nice thread of well-informed comments followed that post and one of the contributors to that thread, Cormac O’Raifeartaigh, is lead author of a paper that has just appeared on the arXiv. It’s quite a lengthy paper (62 pages) that gives an account of the cosmological constant in the context of modern observational cosmology. You can get a PDF of the paper here. It’s well worth reading!

The abstract reads:

We present a centennial review of the history of the term known as the cosmological constant. First introduced to the general theory of relativity by Einstein in 1917 in order to describe a universe that was assumed to be static, the term fell from favour in the wake of the discovery of cosmic the expanding universe, only to make a dramatic return in recent times. We consider historical and philosophical aspects of the cosmological constant over four main epochs: (i) the use of the term in static cosmologies (both Newtonian and relativistic; (ii) the marginalization of the term following the discovery of cosmic expansion; (iii) the use of the term to address specific cosmic puzzles such as the timespan of expansion, the formation of galaxies and the redshifts of the quasars; (iv) the re-emergence of the term in today’s Lamda-CDM cosmology. We find that the cosmological constant was never truly banished from theoretical models of the universe, but was sidelined by astronomers for reasons of convenience. We also find that the return of the term to the forefront of modern cosmology did not occur as an abrupt paradigm shift due to one particular set of observations, but as the result of a number of empirical advances such as the measurement of present cosmic expansion using the Hubble Space Telescope, the measurement of past expansion using type SN 1a supernovae as standard candles, and the measurement of perturbations in the cosmic microwave background by balloon and satellite. We give a brief overview of contemporary interpretations of the physics underlying the cosmic constant and conclude with a synopsis of the famous cosmological constant problem.

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Thelonious Monk, Genius of Modern Music

Posted in Jazz with tags , , , on November 21, 2017 by telescoper

I was delighted to discover that this week’s Composer of the Week on BBC Radio 3 is none other than the great Thelonious Monk, who thoroughly deserves the honour as he was enormously influential as a composer as well as a bandleader and piano soloist. Many of Monk’s highly original compositions – such as Blue Monk, Straight No Chaser, In Walked Bud and ‘Round Midnight– have become jazz standards, but his unique approach to composition really changed the entire evolution of jazz in the immediate post-war era. In fact, Monk is the second-most recorded jazz composer ever, after Duke Ellington (a man he admired enormously and whose piano style influenced Monk’s).

The series of radio programmes about him is particularly timely as this year marks the centenary of his birth (10th October 1917).

In my top 50 jazz albums there would probably be about half a dozen by Thelonious Monk. I’ve loved his music since I heard the very first track by him way back when I was a teenager. Although he has often been given the nickname `The High Priest of Bop’, I’ve never really thought of him as fitting neatly in the bebop style – the archetypal bebop pianist was surely Bud Powell – but he was clearly a profound influence on others of that era, such as Charlie Parker and Dizzy Gillespie. I should add that he was entirely self-taught, which is probably how he managed to get that instantly recognisable sound. You only need to hear one note to know that it’s Monk.

I think the word `genius’ is extremely overused these days, and I tend to reserve it for those who show such an astonishing level of creativity that you think to yourself `Where on Earth did that come from?’. In my opinion it is no exaggeration to apply the word `genius’ to Thelonious Monk. He was a very special artist. Indeed when he was signed up by the fledgling Blue Note label in 1947, they called his first albums Genius of Modern Music..

Anyway, when I listened to yesterday’s programme on iPlayer I remembered this, a compilation of Monk’s advice to band members (as collected by saxophonist Steve Lacy in 1960). As well as being in places very funny, it also contains a great deal of very sound advice for young musicians (especially the first, `Just because you’re not a DRUMMER, doesn’t mean that you don’t have to KEEP TIME’.

I also like `Don’t play the PIANO PART. I’m playing that.’. I’m sure there’s a story behind every one of these tips!

By way of my own little tribute to Thelonious Monk here’s one of my favourite Monk tunes, as recorded with Milt Jackson on vibes way back in 1948. It’s typically offbeat Monk composition, and also provides great examples of him as a soloist and accompanist. Just listen to what he does behind Milt Jackson’s solo on I Mean You, which appeared on Genius of Modern Music Vol. 1…

 

 

 

Antikythera, the Green Island of Science

Posted in History, The Universe and Stuff with tags , , , on November 20, 2017 by telescoper

You’ve probably all heard of the Antikythera Mechanism, a sophisticated device that was used about 2000 years ago by the Greeks to predict astronomical positions and eclipses for calendar and astrological purposes and found in 1902 at the site of a shipwreck near the island of Antikythera. You may not know that there is a strong connection between the study of this amazing piece of machinery and my current employer, Cardiff University, especially through our own Emeritus Professor Mike Edmunds.

Well, it seems that another episode in the story of Antikythera is about to open up as a result of a new initiative of the National Observatory of Athens, in collaboration with the Prefecture of Attica and the Municipality of the island of Kythira. This will lead to the creation of an Observatory of Climate Change and Centre of Geosciences at the island of AntiKythera, where the famous ancient mechanism was found and which is currently almost deserted.

Here is a little video about this project. The dialogue is in Greek, but with subtitles. I should also point out that the first person you see and hear is Manolis Plionis, who is Director of the National Observatory of Athens, a very old friend of mine who I first met at Sussex when I started my graduate studies in the Astronomy Centre there in 1985.

GW170608—The underdog

Posted in The Universe and Stuff with tags , , on November 20, 2017 by telescoper

Interesting post from a gravitational wave researcher, telling the inside story of the latest gravitational wave detection (a binary black hole merger) announced last week.

 

 

Christopher Berry

Detected in June, GW170608 has had a difficult time. It was challenging to analyse, and neglected in favour of its louder and shinier siblings. However, we can now introduce you to our smallest chirp-mass binary black hole system!

Family of adorable black holes The growing family of black holes. From Dawn Finney.

Our family of binary black holes is now growing large. During our first observing run (O1) we found three: GW150914, LVT151012 and GW151226. The advanced detector observing run (O2) ran from 30 November 2016 to 25 August 2017 (with a couple of short breaks). From our O1 detections, we were expecting roughly one binary black hole per month. The first same in January, GW170104, and we have announced the first detection which involved Virgo from August, GW170814, so you might be wondering what happened in-between? Pretty much everything was dropped following the detection of our first…

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Workie Ticket 

Posted in Biographical with tags , , on November 19, 2017 by telescoper

As part of a (very) occasional series of posts relating to words or phrases originating in the North, I thought today I would introduce you to the Geordie expression “workie ticket” (or “worky ticket”), which means a troublemaker or or disruptive or similarly irritating person. 

I believe the expression derives from members of the armed forces who would be deliberately insubordinate or incompetent or misbehave in some other way in order to get themselves discharged and sent home, ie to work their ticket home. 
This phrase was particularly applied to people on National Service, many of whom would rather have been elsewhere and some of whom did their best to get thrown out.It was also used when I was at school in reference to apply to stroppy or disruptive pupils.

I haven’t heard the phrase used in anger (so to speak) for many years, and I don’t know if it is still in common use in Newcastle, but it has popped into my mind on a number of occasions in reference to University staff or students. I couldn’t possibly mention any names…

The threads of an old life

Posted in Biographical, Film with tags on November 18, 2017 by telescoper

 

 

And then there were five….

Posted in The Universe and Stuff with tags , , , , , , on November 17, 2017 by telescoper

…black hole mergers detected via gravitational waves, that is. Here are the key measurements for Number 5, codename GW170608. More information can be found here.

Here is the abstract of the discovery paper:

On June 8, 2017 at 02:01:16.49 UTC, a gravitational-wave signal from the merger of two stellar-mass black holes was observed by the two Advanced LIGO detectors with a network signal-to-noise ratio of 13. This system is the lightest black hole binary so far observed, with component masses 12+7-2 M⊙ and 7+2-2 M⊙ (90% credible intervals). These lie in the range of measured black hole masses in low-mass X-ray binaries, thus allowing us to compare black holes detected through gravitational waves with electromagnetic observations. The source’s luminosity distance is 340 +140-140Mpc, corresponding to redshift 0.07+0.03-0.03. We verify that the signal waveform is consistent with the predictions of general relativity.

This merger seems to have been accompanied by a lower flux of press releases than previous examples…